A method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method

Abstract

The present invention relates to a method for preparing micron-sized spherical covalent organic framework COFs materials by a seed method: dissolving aldehyde organic ligands and amine organic ligands in acetonitrile, adding acetic acid solution and shaking, standing at room temperature for 3-24 h, and obtaining different types of seed crystals; weighing a certain amount of aldehyde organic ligands and amine organic ligands, respectively dissolving them in acetonitrile solution containing acetic acid, and obtaining aldehyde organic ligand growth liquid and amine organic ligand growth liquid; transferring the synthesized seed crystals to a beaker and ultrasonically dispersing them, and then injecting aldehyde organic ligand growth liquid and amine organic ligand growth liquid into the beaker at the same time every 10-60 min, shaking evenly and standing, and repeating the above operation until the COFs spherical particle size reaches the required requirement (3-5 μm). The method solves the technical bottleneck of the current lack of uniform spherical COFs preparation method that meets the chromatographic column packing size requirements (≥ 3 μm), while avoiding the high back pressure problem and promoting compatibility with commonly used chromatographic instruments.

Description

Technical Field

[0001] The invention belongs to the technical field of COFs material preparation, and in particular relates to a method for preparing micron-sized spherical covalent organic framework COFs material by a seed crystal method. Background Art

[0002] Chromatographic separation technology plays an important role in the fields of medicine, analysis, and chemical industry. Among them, chromatographic separation materials are the core of chromatographic separation technology, and their separation performance mainly depends on the chromatographic filling materials. At present, commercial chromatographic filling materials are mainly silica microspheres and polystyrene microspheres. However, silica has insufficient acid and alkali tolerance, especially in alkaline solutions, it is easily corroded and collapsed, and polystyrene microspheres are easy to swell in organic solvents, resulting in insufficient reproducibility. These shortcomings hinder the application of commercial fillers under extreme separation conditions. Therefore, the development of new chromatographic fillers with good chemical stability is of great research significance for promoting industrial production.

[0003] Covalent organic frameworks (COFs) are a class of organic crystalline polymers that are orderly connected by rigid ligands through covalent bonds. They have satisfactory stability, predictable structure and accessible modification. Due to their porous structure, good acid-base stability and low organic solvent swelling, they have been widely studied in the field of chromatographic separation in recent years and have shown great application prospects.

[0004] Recently, different types of COFs materials have been reported for capturing target compounds. Unfortunately, the irregular morphology and submicron (0.1-1 µm) size of COFs particles result in high back pressure in HPLC applications. The pressure of the HPLC system is mainly generated in the chromatographic column (SPE column). If the column pressure is too high, the pressure suddenly decreases after reaching the flow cell of the detector (UV), and the bubbles in the mobile phase expand, which will interfere with the detection and affect the service life of the column. At present, the particle sizes of commercial chromatographic packings for analytical separation are mainly 3, 5 and 10 μm. It has been reported that the particle size of the packing is one of the main factors affecting the back pressure of the packing column. The smaller the particle size, the greater the column pressure. The increase in column pressure limits the practical application of packings with a particle size of less than 3 μm. Therefore, the spherical COFs chromatographic packings synthesized at present with a particle size limited to the submicron (0.1-1 µm) level are difficult to meet the particle size requirements of traditional commercial chromatographic packings (≥ 3 µm), which hinders their commercialization.

[0005] In order to overcome the limitations of the above-mentioned prior art, COFs are usually bonded to the surface of silica particles (SiO2) for SPE sample preparation and chromatographic columns. However, the synthesis of COFs@SiO2 composites requires multiple modifications, which is the main limitation for the application of composite materials in analytical chemistry. Recently, Lin's group proposed a size-controlled synthesis method for spherical COFs with a maximum diameter of 1.3 μm, but its size has always been unable to solve the bottleneck of the particle size demand (≧3 µm) of traditional commercial chromatographic fillers, and is far from meeting the use requirements of chromatographic fillers. In order to break through the technical bottleneck that the existing methods cannot accurately and controllably synthesize micron-sized spherical COFs (≥ 3 µm) that meet the requirements of chromatographic columns, the present invention provides a general method for the controllable preparation of micron-sized (3-5 μm) spherical COFs materials by seed crystal method. Summary of the invention

[0006] The purpose of the present invention is to overcome the technical defects that the particle size of the existing synthetic spherical COFs chromatographic fillers is mainly limited to the submicron level (<1 µm) and it is difficult to meet the requirements of the particle size of traditional commercial chromatographic fillers (≥ 3 µm), and to provide a simple seed method for preparing micron-level (3-5 μm) spherical covalent organic framework COFs materials. This method solves the technical bottleneck of the current lack of uniform spherical COFs preparation methods that meet the chromatographic column filler size requirements (≥ 3 µm), while avoiding the high back pressure problem and promoting the compatibility with commonly used chromatographic instruments, which is a major challenge.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing micron-sized spherical covalent organic framework (COFs) materials by a seed crystal method, wherein a certain amount of aldehyde organic ligands and amine organic ligands are used to synthesize submicron spherical COFs, which are used as seeds, and a seed crystal growth method is used to finally synthesize micron-sized spherical COFs. The specific steps are as follows:

[0009] The steps include:

[0010] 1) Synthesis of seed crystals:

[0011] The aldehyde organic ligand and the amine organic ligand are dissolved in acetonitrile, acetic acid solution is added and rapidly shaken, and then allowed to stand at room temperature for 3-24 h (preferably 12 h) to obtain different types of seed crystals; the size of the seed crystals is 400-850 nm;

[0012] 2) Preparation of growth solution:

[0013] Weigh a certain amount of aldehyde organic ligand and amine organic ligand, and dissolve them in acetonitrile solution containing acetic acid, respectively, to obtain aldehyde organic ligand growth solution and amine organic ligand growth solution;

[0014] 3) Preparation of micron-sized spherical COFs by seed crystal method:

[0015] The seed crystals synthesized in step 1) are transferred to a 100 mL beaker and ultrasonically dispersed (generally, the ultrasonic dispersion time is 1 to 5 min); then, the aldehyde organic ligand growth solution and the amine organic ligand growth solution prepared in step 2) are simultaneously injected into the beaker every 10 to 60 min, and after shaking evenly, the solution is allowed to stand for growth. The aforementioned operation is repeated (i.e., the aldehyde organic ligand growth solution and the amine organic ligand growth solution are repeatedly injected simultaneously, and the solution is allowed to stand after shaking evenly, which generally takes about 2 to 10 days) until the particle size of the spherical COFs material reaches the required 3 to 5 μm.

[0016] Specifically, the aldehyde organic ligand in step 1) is 2,5-divinylterephthalaldehyde, terephthalaldehyde, 2.5-dihydroxyterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, and 2,5-diethynyloxyterephthalaldehyde.

[0017] Specifically, the amine organic ligand in step 1) is 1,3,5-tris(4-aminophenyl)benzene.

[0018] Furthermore, in step 1), 0.03-0.09 mmol of aldehyde organic ligand and 0.02-0.06 mmol of amine organic ligand are dissolved in 4-6 mL of acetonitrile. Preferably, the molar ratio of aldehyde organic ligand to amine organic ligand is 3:2.

[0019] Furthermore, the volume of the acetic acid solution added in step 1) is 0.3-0.8 mL, and the concentration is 10-14 mol / L.

[0020] Specifically, in step 2), the concentration of the aldehyde organic ligand in the aldehyde organic ligand growth solution is 0.006-0.018 mmol / mL.

[0021] Furthermore, in step 2), the concentration of the amine organic ligand in the amine organic ligand growth solution is 0.004-0.012 mmol / mL. In the growth solution of step 2), the molar ratio of the aldehyde organic ligand to the amine organic ligand is 3:2.

[0022] Furthermore, the volumes of the aldehyde organic ligand growth solution and the amine organic ligand growth solution injected in step 3) are 0.1-0.3 mL respectively.

[0023] Specifically, in step 3), after simultaneously injecting the aldehyde organic ligand growth solution and the amine organic ligand growth solution prepared in step 2), the solution needs to be shaken for 1 to 10 seconds and then allowed to stand for 10 to 60 minutes, preferably 30 minutes. The standing time is the interval between the two additions of the growth solution.

[0024] The present invention also provides a micron-sized spherical covalent organic framework COFs material prepared by the above method.

[0025] The present invention uses a general strategy for preparing micron-sized spherical COFs by seed crystal method, which first synthesizes seed crystals; then adds a specific volume of growth liquid to the seed crystals at a certain interval to continue growing; after transferring the synthesized seed crystals to a beaker, the growth liquid is repeatedly added until the required size is obtained. Different aldehyde organic ligands and amine organic ligands can be used to construct micron-sized COFs spheres (3-5 µm) with different physical and chemical properties that meet the chromatographic column size requirements (≥ 3 µm); the synthesized uniform micron-sized COFs spherical particles can be used as filling materials for gas or liquid chromatography columns, materials for separating and enriching trace targets from complex matrices, etc.

[0026] In order to solve the technical bottleneck problem that the currently synthesized spherical COFs chromatographic fillers with particle sizes limited to the submicron level (0.1-1 µm) cannot meet the requirements of the particle size (≥ 3 µm) of traditional commercial chromatographic fillers, which hinders their commercial promotion, spherical COFs were synthesized at room temperature using substances containing amino and aldehyde groups as ligands. Using this as a seed, it was dispersed in an acetonitrile solvent containing an acetic acid catalyst, and then an acetic acid acetonitrile solvent containing a certain concentration of amino and aldehyde ligands was slowly added to the above-mentioned seed solvent, and after oscillation, it was allowed to react at room temperature to synthesize micron-sized (3-5 μm) spherical COFs. The present invention shows that this preparation strategy can be applied to the preparation of micron-sized spherical COFs with various properties, and the prepared uniform micron-sized COFs spherical particles can be used as gas or liquid chromatography column filling materials, materials for separating and enriching trace targets from complex matrices, etc.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention overcomes the technical bottleneck problem that the existing preparation of micron-sized spherical COFs is mainly limited to the submicron level (<1 µm), which is difficult to meet the requirements of the particle size (≥ 3 µm) of traditional commercial chromatographic fillers. The present invention adopts the seed method to controllably synthesize micron-sized spherical COFs particles (3-5 μm). The material has a uniform diameter and spherical morphology, and can be used as a chromatographic column filler and HPLC for separation and analysis of target substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the preparation process of COFs materials of the present invention;

[0030] Figure 2SEM images of the seed COF-V (a) with a size of 0.85 µm and the spherical COF-V target materials with sizes of 2 µm (b), 3 µm (c), and 5 µm (d) prepared in Example 1;

[0031] Figure 3 XRD patterns of the seed COF-V (a) with a size of 0.85 µm and the spherical COF-V target materials with sizes of 2 µm (b), 3 µm (c), and 5 µm (d) prepared in Example 1;

[0032] Figure 4 Infrared spectra of the spherical COF-V target material with a size of 5 µm prepared in Example 1 before treatment and after immersion in different solvents (pH 1 hydrochloric acid, pH 13 NaOH, acetone or water) for 24 h. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0034] In the following examples, all the raw materials used are common commercial products that can be directly purchased. Room temperature refers to 25±5°C.

[0035] Example 1

[0036] A method for preparing micron-sized spherical covalent organic framework COFs materials by seed crystal method (preparation flow chart as shown in Figure 1 The specific steps are as follows:

[0037] 1) Synthesis of seed crystals:

[0038] 0.06 mmol of aldehyde organic ligand 2,5-divinylterephthalaldehyde and 0.04 mmol of amine organic ligand 1,3,5-tri(4-aminophenyl)benzene were weighed and dissolved in 5 mL of acetonitrile, followed by adding 0.3 mL of acetic acid solution (12 M) and rapidly shaking for 5 s, and then standing at room temperature for 12 h to obtain seed crystals of COF-V;

[0039] 2) Preparation of growth solution:

[0040] A certain amount of aldehyde organic ligand 2,5-divinylterephthalaldehyde and amine organic ligand 1,3,5-tri(4-aminophenyl)benzene were weighed and dissolved in acetonitrile solution containing 0.6 mol / L acetic acid to obtain aldehyde organic ligand growth solution and amine organic ligand growth solution; the concentration of aldehyde organic ligand in the aldehyde organic ligand growth solution was 0.012 mmol / mL, and the concentration of amine organic ligand in the amine organic ligand growth solution was 0.008 mmol / mL;

[0041] 3) Preparation of micron-sized spherical COFs by seed crystal method

[0042] Transfer the seed crystals synthesized in step 1) to a 100 mL beaker and disperse them by ultrasonic for 3 min. Then, inject 0.2 mL of the aldehyde organic ligand growth solution and amine organic ligand growth solution prepared in step 2) into the beaker at the same time every 30 min, shake evenly (8 s) and let stand for 30 min, repeat the above operation; the particle size of the spherical COF-V material reaches 2 µm in about 1.5 days, 3 µm in about 2.1 days, and 5 μm in 7 days.

[0043] The present invention measured and characterized the morphology and structure of the target material prepared in the above embodiment, as follows:

[0044] The spherical COF-V target material was prepared by the seed crystal method through the aldehyde-amine condensation reaction of 2,5-divinylterephthalaldehyde (DVA) organic ligand and 1,3,5-tri(4-aminophenyl)benzene (TPB) organic ligand. Its size, morphology and uniformity were measured by scanning electron microscopy, and its structure was determined by X-ray powder diffraction.

[0045] The present invention is a scanning electron microscope image of the spherical COF-V target material (see Figure 2 ) and X-ray powder diffraction (see Figure 3 ) were analyzed. Figure 2 As shown in a, when the volume of acetic acid added is 0.3 mL as described in Example 1, the size of the seed COF-V is 850 nm; after repeated growth, the size of the spherical COF-V target material can be precisely controlled to 2 µm ( Figure 2 middle b), 3 µm ( Figure 2 c) and 5 µm ( Figure 2 (d) Figure 2 It shows that the spherical COF-V target material prepared by the seed crystal method has a spherical morphology and good uniformity.

[0046] Figure 3 In the XRD patterns of the materials at the four sizes measured, all have sharp peaks, indicating that the prepared spherical COF-V target material has excellent crystallinity. Figure 3 In the diffraction pattern of COF-V, the diffraction peaks at 2.70°, 4.76°, 5.50° and 7.32° are respectively attributed to the (100), (110), (200) and (210) planes of the material. The experimental spectrum obtained by X-ray powder diffraction analysis of the target material is basically consistent with the theoretical spectrum of single crystal diffraction analysis, indicating that the synthesized sample is pure. Figure 4It can be seen that its infrared spectrum is at 1606 cm -1 A −C=N peak appeared at , indicating that the amino group of TPB and the aldehyde group of DVA successfully underwent a condensation reaction.

[0047] The present invention evaluates the stability of the spherical COF-V target material by means of IR testing. After the material is immersed in different solutions (pH 1 hydrochloric acid, pH 13 NaOH, acetone or water) for 24 hours, its IR peak value does not change significantly (see Figure 4 ), indicating that the material has good stability, making it more widely used in many fields.

[0048] Example 2

[0049] A method for preparing micron-sized spherical covalent organic framework COFs materials by seed crystal method, the specific steps are as follows:

[0050] 1) Synthesis of seed crystals:

[0051] Weigh 0.06 mmol of aldehyde organic ligand 2.5-dihydroxyterephthalaldehyde and 0.04 mmol of amine organic ligand 1,3,5-tri(4-aminophenyl)benzene respectively, and then dissolve them in 5 mL of acetonitrile, then add 0.3 mL of acetic acid solution (12M) and shake rapidly for 5 s, then stand at room temperature for 12 h to obtain seed crystals;

[0052] 2) Preparation of growth solution:

[0053] A certain amount of aldehyde organic ligand 2.5-dihydroxyterephthalaldehyde and amine organic ligand 1,3,5-tri(4-aminophenyl)benzene were weighed and dissolved in acetonitrile solution containing 0.6 mol / L acetic acid to obtain aldehyde organic ligand growth solution and amine organic ligand growth solution; the concentration of aldehyde organic ligand in the aldehyde organic ligand growth solution was 0.012 mmol / mL, and the concentration of amine organic ligand in the amine organic ligand growth solution was 0.008 mmol / mL;

[0054] 3) Preparation of micron-sized spherical COFs by seed crystal method

[0055] The seed crystals synthesized in step 1) were transferred to a 100 mL beaker and ultrasonically dispersed for 3 min. Then, 0.2 mL of the aldehyde organic ligand growth solution and amine organic ligand growth solution prepared in step 2) were injected into the beaker every 30 min, and the mixture was shaken evenly (8 s) and allowed to stand for 30 min. The above operation was repeated until the COFs spheres reached the required particle size of 5 μm in 7 days.

[0056] Example 3

[0057] The difference from Example 1 is that in step 1), the aldehyde organic ligand 2,5-divinylterephthalaldehyde is replaced by 2,5-dimethoxyterephthalaldehyde.

[0058] Example 4

[0059] The difference from Example 1 is that in step 1), the aldehyde organic ligand 2,5-divinylterephthalaldehyde is replaced by terephthalaldehyde.

[0060] Example 5

[0061] The difference from Example 1 is that in step 1), the aldehyde organic ligand 2,5-divinylterephthalaldehyde is replaced by 2,5-diethynyloxyterephthalaldehyde.

[0062] In summary, the present invention adopts the seed method to controllably synthesize spherical COFs particles with a particle size of 3 to 5 μm. The material has a uniform diameter and a spherical morphology, and can be used as a chromatographic column filler in conjunction with HPLC for separation and analysis of target substances, overcoming the technical defect that the existing preparation of micron-sized spherical COFs is mainly limited to the submicron (<1 µm) level.

Claims

1. A method for preparing micron-sized spherical covalent organic framework COFs materials by seed crystal method, characterized in that: The steps include: 1) Synthesis of seed crystals: The aldehyde organic ligand and the amine organic ligand are dissolved in acetonitrile, an acetic acid solution is added and shaken, and then allowed to stand at room temperature for 3-24 hours to obtain different types of seed crystals; 2) Preparation of growth solution: Weigh a certain amount of aldehyde organic ligand and amine organic ligand, and dissolve them in acetonitrile solution containing acetic acid, respectively, to obtain aldehyde organic ligand growth solution and amine organic ligand growth solution; 3) Preparation of micron-sized spherical COFs by seed crystal method: The seed crystals synthesized in step 1) are transferred to a beaker and dispersed by ultrasonication; then, the aldehyde organic ligand growth solution and the amine organic ligand growth solution prepared in step 2) are simultaneously injected into the beaker every 10-60 min, shaken evenly and allowed to stand, and the above operation is repeated until the particle size of the spherical COFs material reaches the required requirement; The aldehyde organic ligand in step 1) is 2,5-divinylterephthalaldehyde, terephthalaldehyde, 2.5-dihydroxyterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-diethynyloxyterephthalaldehyde; The amine organic ligand in step 1) is 1,3,5-tris(4-aminophenyl)benzene; In step 1), 0.03-0.09 mmol of aldehyde organic ligand and 0.02-0.06 mmol of amine organic ligand are dissolved in 4-6 mL of acetonitrile.

2. The method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method according to claim 1, characterized in that: The volume of the acetic acid solution added in step 1) is 0.3-0.8 mL, and the concentration is 10-14 mol / L.

3. The method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method according to claim 1, characterized in that: In step 2), the concentration of the aldehyde organic ligand growth solution is 0.006-0.018 mmol / mL.

4. The method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method according to claim 1, characterized in that: In step 2), the concentration of the amine organic ligand growth solution is 0.004-0.012 mmol / mL.

5. The method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method according to claim 1, characterized in that: The volumes of the aldehyde organic ligand growth solution and the amine organic ligand growth solution injected in step 3) are 0.1-0.3 mL respectively.

6. The method for preparing micron-sized spherical covalent organic framework COFs material by seed crystal method according to claim 1, characterized in that: In step 3), shake for 1 to 10 seconds and then let it stand.

7. Micron-sized spherical covalent organic framework (COFs) material prepared by the method according to any one of claims 1 to 6.

Images